In order to suppress disturbance of a photographed image due to a shake in an optical unit for photographing or the like, a structure has been proposed in which an optical module is structured as a movable module that is capable of being swung and a shake is corrected by swinging the movable module so as to correspond to the shake. For example, a structure has been proposed in which a movable module is swingably supported by a pivot provided on a rear side in an optical axis direction of the movable module and the movable module is swung with the pivot as a swing center so as to correct a shake of an optical unit (see, Japanese Patent Laid-Open No. 2010-96805 and Japanese Patent Laid-Open No. 2010-96863).
In a case of a structure that the movable module is swingably supported by a pivot provided on a rear side in an optical axis direction, a relatively small shake can be corrected but it is difficult to correct a large shake sufficiently.
In order to solve the problem, the present inventor has considered that a movable module is swingably supported by a gimbal mechanism with the use of a movable frame having elasticity, and that posture of the movable module is held by a spring member connected with the movable module and a support body. However, when two members having elasticity (movable frame and spring member) are used, the movable module has a plurality of natural vibration frequencies. As a result, when the optical module is mounted on a movable body such as a vehicle or a radio-controlled helicopter, the natural vibration frequencies of the movable module (natural vibration frequency of the movable frame and natural vibration frequency of the spring member) are overlapped with the vibration frequency band of the movable body and thus the movable module is resonated by vibration of the movable body.
For example, as shown in FIG. 10B, since a spring member holds a posture of the movable module, the spring member has a natural vibration frequency “fb′” of about 60 Hz in a tilt direction (swing direction) and the optical unit has a high gain for shake correction in a frequency band which is lower than the natural vibration frequency in the tilt direction. Further, the movable frame has a natural vibration frequency “fa1′” of about 120 Hz in an optical axis direction (upper and lower shift direction) and a natural vibration frequency “fa2′” of about 330 Hz in a lateral shift direction which is perpendicular to the optical axis direction. Therefore, there is a difference of 60 Hz between the natural vibration frequency “fb′” and the natural vibration frequency “fa1′”. Accordingly, if a width of the vibration frequency band “fw′” is about 50 Hz when photographing is performed by the optical unit while the movable body such as a vehicle or a radio-controlled helicopter is moved, the vibration frequency band “fw′” is not overlapped with the natural vibration frequency “fb′” (about 60 Hz) in the tilt direction (swing direction) of the spring member and the natural vibration frequency “fa1′” (about 120 Hz) in the optical axis direction (upper and lower shift direction) of the movable frame. However, in the movable body such as a vehicle or a radio-controlled helicopter, photographing is performed by the optical unit while being accelerated or decelerated and thus a width of the vibration frequency band “fw′” may become 65 Hz. In this case, the vibration frequency band “fw′” of the movable body is overlapped with the natural vibration frequency “fb′” (about 60 Hz) in the tilt direction (swing direction) of the spring member and the natural vibration frequency “fa1′” (about 120 Hz) in the optical axis direction (upper and lower shift direction) of the movable frame and thereby the movable module is resonated.
In order to prevent the resonance, it may be structured that the optical module is mounted on the movable body through a buffer member, a buffer mechanism or the like. However, in this structure, much labor may be required for mounting the optical module on the movable body.